The present invention relates to improvements in an automatic document feeder used for a recording device or an image reading device provided in an electrophotographic copying apparatus, and more particularly relates to improvements in a circulation type automatic document feeder having a document feeding mode of ADF or R-ADF in which one-sided or two-sided documents stacked on a document stack section are separated from the document stack one by one and fed to an image reading section and then the documents are discharged onto a discharging tray. Further, the present invention relates to improvements in a circulation type automatic document feeder having a one-sided document circulation conveyance mode (RDH mode) in which a read document is returned to the document stack section so that it can be repeatedly fed. Furthermore, the present invention relates to improvements in a circulation type automatic document feeder having a two-sided document reversal circulation conveyance mode (R-RDH mode), a computer form feeding mode (CFF mode), and a manual feeding document feed mode.
An automatic document feeder (ADF) that can efficiently and automatically feed a document on which an image is recorded, has already been provided to a recording device installed in an electrophotographic copying apparatus or a recorded image reading apparatus.
An automatic document feeder (R-ADF) having a reversal function by which a document is reversed, is put into practical use as a copying apparatus by which the images on a two-sided document are copied onto one side or both sides of a recording sheet and as an image reading apparatus by which the images are read.
Also, a circulation type automatic document feeder (RDH) has been proposed in which the documents stacked on a document stack section are separated one by one and automatically fed onto a platen glass and the document exposed to light on the platen glass is returned to the document stack section so that the document can be repeatedly processed. By this circulation type automatic document feeder (RDH), a copy is made when a document is circulated once, so that the document is circulated by the number of required copies. For example, the above technique is disclosed in Japanese Patent Publication Open to Public Inspection Nos. 179466/1986 (U.S. appln No. 678861, Priority date: Dec. 6, '84) and 183031/1986 (U.S. appln No. 678863, Priority date: Dec. 6, '84).
Moreover, a circulation type automatic document feeder (R-RDH) has been also provided in which a document reversal mechanism is added to the RDH described above (disclosed in Japanese Patent Application Open to Public Inspection No. 197246/1989).
With these circulation type automatic document feeders (RDH and R-RDH), which will be referred to as RDH hereinafter, it is possible to conduct a high speed continuous copying operation and to quickly collate copied recording sheets. Moreover, when the circulation type automatic document feeder (RDH) is combined with a finisher device by which stapling and punching operations are conducted on the recording sheets, the overall recording operation can be automatically performed.
Recently, there is provided an automatic document feeder having a continuous sheet conveyance device by which a perforated and folded continuous sheet can be conveyed, wherein this perforated and folded continuous sheet is referred to as a computer output fan folded sheets, a continuous sheet document or a CCF document in this specification, hereinafter.
However, the following problems may be encountered in the above conventional automatic document feeder.
(1) When a CCF document feeder is provided in the above automatic document feeder, the construction becomes complicated, so that the size and weight of the feeder are increased. Accordingly, it is difficult for an operator to handle the automatic document feeder when he lifts it to open the platen glass surface. Therefore, the operation of jam clearance becomes difficult, and further it requires much labor.
In the above automatic document feeder, there are provided a pair of rollers for inverting documents in the sheet discharging section. In this case, an upper roller on the drive side and a lower roller on the idle side are separately attached onto the automatic document feeder side and the apparatus main body side. Therefore, when the automatic document feeder is set on the copying apparatus main body, the pair of rollers can not be accurately aligned, and a positional error is created, so that a nip line formed by the upper and lower rollers fluctuates, and conveyed documents are skewed.
(3) Conventionally, the pair of rollers for inverting the document and a pair of rollers provided on the upstream side of document conveyance are located on the same horizontal line. Accordingly, when a curled document is switched back, it is caught by a gate member for changing over a conveyance passage. Therefore, the document is jammed, and it can not be appropriately inverted.
(4) In general, a sheet discharging tray provided in the sheet discharging section of the automatic document feeder is thin and long, and supported by and protruded from a casing of the automatic document feeder in the manner of a cantilever. Accordingly, the sheet discharging tray tends to be bent. For this reason, when a large number of documents (for example, about 100 sheets of documents) are stacked on the sheet discharging tray, it is deformed by the weight of documents. Therefore, the stacked documents are not appropriately aligned. Further, when a force is mistakenly applied to this protruded sheet discharging tray, it may be damaged.
(5) In the case where upper and lower sheet discharging trays are provided in the automatic document feeder, a CFF document is sent to a sheet discharging passage between the upper and lower sheet discharging trays. In this construction, the upper sheet discharging tray and gate plate must be withdrawn in the case of jam clearance. Accordingly, the structure becomes complicated, and the reliability of document conveyance is deteriorated.
(6) According to this structure, in the case where a CFF document is discharged, an upper portion of the sheet discharging tray is open, and there is no member to guide the document. As a result, the CFF document jumps out from the sheet discharging tray, and can not be appropriately folded.
(7) There is provided a copying machine constructed in such a manner that a sorter is attached onto the side and CFF documents are discharged from the sheet discharge section to the sorter, and a CFF document tray is disposed on the outside of the sorter. According to the above structure, the installation space is increased, and further the number of parts is increased for installing the CFF document tray, which raises the manufacturing cost.